1. Field of the Invention
The present invention relates to copper precursor compositions and their synthesis, and to a method for production of copper circuits in microelectronic device structures, as for example in formation of metal interconnects for the manufacture of semiconductor integrated circuits, thin-film recording heads and packaging components, or otherwise for metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such precursor compositions. The precursor compositions of the invention are also usefully employed for forming seed layers of copper for subsequent electroless or electrochemical plating of copper and other metals.
2. Description of the Related Art
The process of fabricating semiconductor integrated circuits generally includes the formation of metal interconnect lines. The metal interconnect lines often may be formed from multiple conductive layers. For example, a thin conductive layer generally termed a barrier layer may be formed from a metal, metal nitride, metal silicide, or metal silicon nitride and a thicker conductive layer, e.g., composed of aluminum, may be formed on the barrier layer.
In order to enhance circuit speed performance and reduce the resistance-capacitance (RC) signal delay, the use of copper layers has been proposed and implemented to replace the use of aluminum layers, wherein one or more metal layers of a semiconductor integrated circuit may be formed utilizing a copper based layer. Copper is of great interest for use in metallization of VLSI devices because of its low resistivity, low contact resistance, and ability to enhance device performance through the reduction of RC time delays. Many semiconductor device manufacturers are adopting copper metallization for use in production of microelectronic chips, thin-film recording heads and packaging components.
Chemical vapor deposition (CVD) of copper provides uniform coverage for the metallization. Liquid CVD precursors and/or solid precursors dissolved into solvents or excess ligands enable direct injection and/or the liquid delivery of precursors into a CVD vaporizer unit. The accurate and precise delivery rate can be obtained through volumetric metering to achieve reproducibility in CVD metallization of in VLSI device manufacturing.
Currently only a few liquid copper precursors are commercially available. These include (hfac)Cu(MHY), (hfac)Cu(3-hexyne), (hfac)Cu(DMCOD) and (hfac)Cu(VTMS), wherein hfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne, DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane.
In order to prevent detrimental effects which may be caused by the interaction of a copper layer with other portions of the integrated circuit, a barrier layer is typically utilized in conjunction with copper layers. Any of a wide range of barrier materials may be utilized including materials comprising metals, metal nitrides, metal suicides, and metal silicon nitrides. Exemplary barrier materials include titanium nitride, titanium silicide, titanium silicon nitrides, niobium nitrides, niobium silicon nitrides, tantalum nitride, tantalum silicide, tantalum silicon nitrides, tungsten nitride, tungsten silicide and tungsten silicon nitride. After the formation of a barrier layer, the copper is deposited on the barrier layer. The initial copper deposition may function as an adhesion seed layer, an electrochemical or CVD seed layer, and the initial copper deposition may be followed by electrochemical plating or CVD of copper. Alternatively, the copper deposition may be employed to fully deposit the desired amount or thickness of copper.
The use of various copper precursors in CVD reactors to create copper interconnects in semiconductor integrated circuits, for example, is well known. See, for instance, U.S. Pat. Nos. 5,085,731; 5,098,516; 5,144,049; and 5,322,712; and the references cited in those patents. New and useful compositions and processes for the production of copper that improve on, or provide alternatives to, these known compositions would be highly desirable and embody a significant advance in the art.
In this respect, copper CVD processes suitable for large-scale manufacture of integrated circuits are extremely valuable to the electronics industry. Towards these ends, copper CVD can be used in two ways:
1. deposition of an adherent and conductive thin-film layer as a plating base for electroplating processes.
2. full-fill deposition of copper interconnects, thin-film circuitry, recording head coils and other features.
In electroplating applications, several critical features must be achieved in the deposition of the plating base, or xe2x80x9cseedxe2x80x9d layer, for the subsequent electroplating to be successful. The deposition of a useful xe2x80x9cthin-film seed layerxe2x80x9d must satisfy the following film requirements:
1. The film requires low resistivity and uniform thickness, thereby allowing uniform current densities to be realized during plating.
2. The film requires uniform conformality in high aspect ratio features to satisfy complex device geometries, multi-level metal layers and damascene processing.
3. The film must exhibit excellent adhesion between the deposited copper metallurgy and the barrier layer, and between subsequent levels of metal interconnect metallurgy.
In an attempt to achieve these results, copper precursor alternatives to the current commercial materials, such as (hfac)Cu(vinyltrimethylsilane), commercially available as CupraSelect (Schumacher Division of Air Products and Chemicals, Inc., Allentown, Pa.) are badly needed. (Hfac)Cu(vinyltrimethylsilane), suffers from inherent thermal instability and therefore requires additives to enhance the molecule""s physical properties, including thermal stability, and to facilitate uniform nucleation and film growth. Further, these chemical additives can induce process complexities and negatively alter device integration, such as by creating high contact resistances due to contamination of contacting surfaces (with fluorine and/or oxygen impurities).
For example, one additive that has been employed is hexafluoro-2,4-pentanedionate hydrate. The addition of such a hydrate to the vinyltrimethylsilane Cu(hfac), or corresponding addition of small amounts of water, has generally been found to substantially increase the deposition rate of the CVD process. Such additives, however, may lead to contamination of the interfacial surface regions and/or copper film, either during nucleation or steady-state film growth. In both cases, the electrical properties of the film or contact region may be compromised, resulting in high film resistivity and/or high contact resistance. In multi-layered structures, both of these electrical properties are critical in respect to device integration and manufacture.
Such contamination of the product film incident to the use of hfac-hydrate in the CVD formulations is attributable to the fact that hfac is susceptible to decomposition during the film growth process especially at the barrier-copper interface. In fact, Hhfac has been used to attack and etch metal surfaces, showing a strong tendency to remain on the surface of the barrier layer and/or copper nucleation layer during subsequent metallization. In addition, over time precursors such as vinyltrimethylsilane Cu(hfac) show decomposition to green Cu(II) species. Thus, the inherent thermal instability of this precursor and the required chemical additives pose significant deficiencies in the prior and current art. There is, therefore, a significant need in the art for copper formulations that deliver improved copper precursors to the CVD process without undesirable side effects. There is particularly a need for formulations that exhibit greater thermal stability without undesirable side effects due to the presence of fluorine substituents and/or aging of the precursor solution.
Alternative commercial alkyne and ene-yne Cu(I)(hfac) precursors are volatile and afford rapid deposition rates, but these compounds are also susceptible to thermal decomposition during heating, and they may form dinuclear complexes with decreased thermal stability and/or volatility. In both cases, the deposition rate may drop and hinder the ability to achieve xe2x80x9cfull-fillxe2x80x9d metallization, so that the utility of these precursors is diminished for full-scale manufacturing of copper interconnects and copper-based devices. A method is therefore desired to circumvent this deficiency in the provision of improved precursors and formulations that are amenable to liquid delivery CVD.
Additionally, currently available precursors for copper CVD are quite expensive. To reduce the cost of copper metallization, inexpensive precursors need to be developed. In this regard, low cost ligands are required to lower the cost-of-ownership (COO) and provide an economic capability for manufacturing copper-based devices.
There is therefore a need in the art for new and improved copper precursors for metallization in the manufacture of integrated circuits and other microelectronic device structures, and for manufacturing thin-film recording heads, copper circuitry and packaging components, using techniques such as chemical vapor deposition, plasma-assisted CVD, plating, etc.
It is accordingly an object of the present invention to provide new copper precursors and formulations.
It is another object of the invention to provide methods of forming copper in the manufacturing of integrated circuits and other microelectronic device structures.
It is a further object of the invention to provide metallization technology for forming interconnects and other device structures that overcome the shortcomings and limitations of the prior art, including improved adhesion, improved contact resistances, improved film resistivities and improved device integration.
It is another object of the invention to provide a method of metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such novel copper precursor compositions.
It is a further object of the invention to provide adherent thin-films for seeding electroless and/or electrochemical plating solutions and to overcome the shortcomings and limitations of the prior art, including improved adhesion, improved contact resistances, improved films resistivities, improved plating, improved conformality, improved manufacturing, and improved device integration.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention comprises a variety of aspects, features and embodiments, as will be more fully apparent from the ensuing disclosure and appended claims.
One aspect of the invention relates to a novel copper precursor composition hfac(Cu)Lx, wherein x is selected from the group consisting of xc2xd and 1 and L is a low-cost ligand selected from the group consisting of alkene, alkyne and combinations thereof.
Another aspect of the invention relates to a novel precursor composition formulation, including a novel copper precursor composition, having the formula (hfac)Cu(L)x, wherein x is selected from the group consisting of xc2xd and 1 and L is a low-cost ligand selected from the group consisting of alkene, alkyne and combinations thereof, in formulation with one or more low-cost ligands selected from the group consisting of alkenes, alkynes, dienes and combinations thereof, to provide increased thermal stability to the formulation and improved vaporization to the CVD reactor.
Compositions of the invention provide unexpected improvements, e.g., increase in deposition rate, improvement in quality of copper, improved thin-film adhesion, reduction in copper impurities, reduction in problems associated with copper precursor decomposition that may detrimentally occur during delivery and transport to the reactor e.g., Cu(I) precursors to Cu(II) compounds, etc.
In another respect, the invention relates to a process for the production of copper, comprising subjecting a precursor composition to chemical vapor deposition, wherein the precursor composition comprises a novel copper precursor having the formula (hfac)Cu(L)x, wherein x is selected from the group consisting of xc2xd and 1 and L is selected from the group consisting of alkene, alkyne and combinations thereof.
In another respect, the invention relates to a process for the production of copper, comprising subjecting a precursor formulation, to chemical vapor deposition, wherein the precursor formulation comprises a novel copper precursor in formulation with one or more low-cost additives, selected from the group consisting of alkene, alkyne, diene and combinations thereof, to provide increased thermal stability to the formulation.
Other aspects of the invention relate to the copper made by the process of this invention as well as integrated circuits, thin-film recording heads and/or packaging components made using the process of this invention.
The precursor compositions of this invention are usefil for the manufacture of copper, including copper interconnects for integrated circuits, thin-film recording heads and/or packaging components.
A further aspect of the invention relates to [(hfac)Cu]2(DMDVS), and to a method of forming copper by vaporizing [(hfac)Cu]2(DMDVS) (wherein DMDVS=dimethyldivinylsilane), as well as to a method of forming a seed layer comprising liquid injection or direct liquid vaporization of [(hfac)Cu]2(DMDVS). In a further method aspect, the invention contemplates a method of making [(hfac)Cu]2(DMDVS), comprising at least one of the following reactions (1) and (2):
Cu2O+2(hfac)H+Lxe2x86x92[(hfac)Cu]2L+H2Oxe2x80x83xe2x80x83(1)
2CuCl+2(hfac)Na+Lxe2x86x92[(hfac)Cu]2L+2NaClxe2x80x83xe2x80x83(2)
wherein L is DMDVS. Interestingly, when using the DMDVS ligand, hfac may be replaced with tfac, wherein tfac is 1,1,1-trifluoroacetylacetonate, or other lower cost xcex2-diketonate ligand. This approach is advantageous for reducing the potential for fluorine contamination by reducing the number of fluorine atoms in the precursor molecule. This achievement of a useful, economic copper precursor having a relatively low fluorine content is a further feature and advantage of this invention.
A further aspect of the invention relates to [(hfac)Cu]2(DMDVS) in formulation with one or more low-cost additives, selected from the group consisting of, alkene, alkyne, diene and combinations thereof, to provide increased thermal stability to the formulation.
Another aspect of the invention relates to a method of forming a plating base or seed layer on a substrate for subsequent electroplating, comprising depositing on the substrate a layer of copper-containing material by liquid delivery chemical vapor deposition using a liquid-phase copper precursor that is thermally stable at liquid delivery vaporization temperatures, to form the layer of copper-containing material as the plating base seed layer.
A still further aspect of the invention relates to a microelectronic device structure comprising a substrate having a chemical vapor deposited copper plating base seed layer on the substrate, wherein the copper plating base seed layer has been formed using a liquid-phase copper precursor that is thermally stable at vaporization temperatures.
Another aspect of the invention relates to a method of full-fill copper metallization of a microelectronic device structure, comprising liquid delivery chemical vapor deposition of copper on the microelectronic device structure. The copper precursor for such full-fill metallization, may therefore comprise a novel copper precursor of the formula (hfac)Cu(L)x, wherein x is selected from the group consisting of xc2xd and 1 and L is a ligand selected from the group consisting of alkene, alkyne and combinations thereof. Specific examples of alkyne ligands embodied in the current invention include, but are not limited to ene-yne, diyne, diene-yne, amine-yne, keto-yne and alkyne. Such novel precursor compositions may be used alone or in formulation with a low cost stabilizer additive selected from the group consisting of alkene, alkyne, diene and combinations thereof.
Yet another aspect of the invention relates to a formulation including the novel copper precursor composition (hfac)Cu(L)x, described hereinabove, in formulation with an additive, wherein the additive provides added thermal stability and comprises a low cost ligand selected from the group consisting of:
(a) alkenes: 
wherein R1, R2, R3 or R4 may be the same as or different from one another, and are independently selected from H, aryl, perfluoroaryl, C1-C8 alkyl or open-chain alkyl, C1-C8 perfluoroalkyl, and C5-C6 cycloalkyl;
(b) alkynes:
R2xe2x80x94xe2x89xa1xe2x80x94R1
wherein R1, and R2 may be the same or different and are independently selected from H, aryl, perfluoroaryl, C1-C8 alkyl, C1-C8 perfluoroalkyl, vinyl, and C1-C6 cyclo-alkyl;
(c) dienes: 
wherein R1, R2, R3, R4, R5 and R6 may be the same or different and are independently selected from H, and C1-C3 alkyl and wherein n=0, 1,2,3 or 4;and
(d) combinations of the foregoing, e.g., alkene, alkyne, diene, keto-yne, etc.
A further aspect relates to a method of forming copper thin films comprising vaporizing a precursor formulation comprising a novel copper precursor composition (hfac)Cu(L)x, wherein x is selected from the group consisting of xc2xd and 1 and L is a low cost ligand selected from the group consisting of alkene, alkyne and combinations thereof, in formulation with an additive of the above-described type.
A still further aspect of the invention relates to a novel copper precursor formulation comprising a novel copper precursor composition selected from the group consisting of
(A) [(hfac)Cu]2(DMDVS);
(B) [(tfac)Cu]2(DMDVS);
(C) (hfac)Cu(DMCOD)
(D) (hfac)Cu(MHY); and
(B) (hfac)Cu(L)x wherein x is selected from the group consisting of xc2xd and 1 and L is a low-cost ligand selected from the group consisting of alkene, alkyne and combinations thereof,
in formulation with a low-cost additive selected from the group consisting of:
(I) alkenes: 
wherein R1, R2, R3 or R4 may be the same as or different from one another, and are independently selected from H, aryl, fluoroaryl, perfluoroaryl, C1-C8 alkyl or open-chain alkyl, C1-C8 fluoroalkyl, C1-C8 perfluoroalkyl, and C5-C6 cycloalkyl;
(II) alkynes of the formula:
R2xe2x80x94xe2x89xa1xe2x80x94R1
wherein R1, and R2 may be the same or different and are independently selected from H, aryl, fluoroaryl, perfluoroaryl, C1-C8 alkyl, C1-C8 fluoroalkyl, C1-C8 perfluoroalkyl, vinyl, and C5-C6 cycloalkyl;
(III) dienes of the formula: 
wherein R1, R2, R3, R4, R5, and R6 may be the same or different and are independently selected from H, and C1-C3 alkyl and wherein n=0, 2, 3 or 4; and
(IV) combinations of the foregoing, e.g., alkene, alkyne, diene, keto-yne, etc.
Another aspect of the invention relates to a method of forming a copper-containing material on a substrate, comprising vaporizing a copper precursor composition or formulation to form a precursor vapor, and contacting the precursor vapor with a substrate to form the copper-containing material thereon.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.